Interpretive Summary: Pesticide application is a major component of peanut production costs in the southeastern United States. Pest management guidelines provide little information that is helpful to peanut growers in selecting appropriate pesticide delivery methods because recommendations are for constant rates applied over the whole growing season. Regular flat fan pattern nozzles are recommended for spraying herbicides to control weeds. This type of nozzle is also commonly used to discharge insecticides and fungicides to peanut canopies to avoid having to change nozzles frequently. However, the spray penetration in peanut canopies during the high vegetative growth stages is very poor with the flat fan nozzles. Four different types of hydraulic nozzle tips were evaluated to improve spray penetration into peanut canopies planted with single-row and twin-row patterns during three growth stages. Spray deposits discharged from the four nozzles decreased dramatically from the top to the bottom of canopies, and also tended to linearly decrease as leaf area index increased. During the three peanut growth stages, the TurboDrop nozzle had the best spray penetration performance, followed by the twin jet, hollow cone nozzles and then the regular flat fan nozzle. Using the TurboDrop nozzle instead of the flat fan nozzle to apply chemicals into peanut canopies could greatly reduce amount of pesticide for peanut insect and disease control.

Technical Abstract:
The spray penetration into peanut canopies with single-row and twin-row planting patterns at three growth stages was investigated with four different types of hydraulic nozzle tips (flat fan, hollow cone, twin jet and TurboDrop). The nozzles were operated at 276 kPa pressure, 6.4 km/hr travel speed, and 0.5 m above the top of canopies. The canopy leaf area index (LAI) and height were measured for each test and correlated with spray deposits at the bottom and middle of peanut canopies. Spray deposits at the top, middle and bottom of canopies were determined with a spray mixture containing water and fluorescein tracer. The concentration of spray samples were corrected with the calibration of the photo degradation of the tracer exposed to direct sunlight, under artificial shade and in a dark room. Plants with single-row and twin-row planting patterns received significantly different spray deposits within peanut canopies. For all four nozzles during the growth season, the spray deposits decreased dramatically from the top to the bottom of canopies, and also tended to linearly decrease as LAI increased. Compared to the flat fan nozzle at the bottom of canopies at 75 days after planting, the TurboDrop nozzle produced 2.6 times higher spray deposits for single-row plants and 1.6 times higher spray deposits for twin-row plants. During the three growth stages, the TurboDrop nozzle produced the highest mean spray deposit at the bottom of canopies, followed by the twin jet and then hollow cone nozzles. The regular flat fan nozzle had the lowest spray penetration performance among the four types of nozzles.